The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Optical recording devices are used to store information, such as music, movies, pictures, data, etc., on recordable media. Examples of recordable media are compact discs (CDs), digital versatile/video discs (DVDs), high density/high definition DVDs and Blu-ray Discs (BDs). In order to record and read such information, operation of a read/write head is controlled to track the location and focus of a laser beam on the recordable media.
In an optical drive the laser beam is moved while an optical storage medium is rotated about a spindle axis. The laser beam is shaped and focused to form a spot over land/groove structures of the optical storage medium via lens actuators. The light from the laser beam is reflected off of the optical medium and directed back into a read/write head. The reflected light is redirected and focused into a spot over a photo-detector integrated circuit (PDIC).
To control the positioning, tracking, and focusing of the laser beam, various servo control computations are performed on information that is collected from the PDIC. The servo control computations provide different tracking and focusing characteristic information including tracking error and focusing error. The servo control computations also include the generation of compensation signals for correction of the errors.
The servo control computations are performed by and can consume up to approximately 90% of the operating time of a processor of the optical drive. This significantly limits the ability of the processor to perform other tasks and thus also limits the operating speed of the optical storage medium.